The Conservancy seem to have glossed over this point. It is not obvious to me. If Canonical were to distribute two, CDs, tarballs, whatever, with Linux on one and ZFS.ko on the other, with a script to load ZFS.ko at install time would _that_ be different?
How about if they distribute Ubuntu on one CD, the ZFS source on the other and a script that builds and loads ZFS.ko at install time? Would _that_ be legal?
If you can distribute linux with binary blob graphics drivers I don't see a big difference with a filesystem module.